Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Separator – retainer or spacer insulating structure
Patent
1992-08-13
1994-06-14
Kalafut, Stephen
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Separator, retainer or spacer insulating structure
429248, H01M 216
Patent
active
053209168
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a separator for alkali-zinc battery for use in a portable equipment power source, a portable power source and an electric vehicle power source etc.
BACKGROUND ART
The alkali-zinc battery has a high energy density and a high power characteristic. Because of a high solubility of zinc, however, zinc acid ions existing in electrolyte at the time of charging have deposited on an anode in dendrite form or spongy form, a short-circuiting piercing through the separator has taken place, or a shape change has occurred to minimize utilization factor; so that a cycle life of a battery has been short.
A micro-porous membrane comprising polypropylene, polyethylene etc. subjected only to surface active agent treatment has been used for a conventional separator for alkali-zinc battery. Such a separator has a desirable property for use in a sealed-type battery in which O.sub.2 gas is absorbed by a zinc electrode, because O.sub.2 gas is permeable through it. However, since it is subjected only to the surface active agent treatment, its hydrophilic property is weakened while it is immersed in electrolyte. Further, a mechanism wherein ZnO is gradually precipitated in micro-pores to bring about short-circuiting, i.e. a dendrite short-circuiting, can not be avoided sufficiently so that it is not suitable for an application requiring a long-term storage or a charge/discharge cycle life of a long period.
In order to improve the above disadvantages, there has been used a separator fabricated by a semi-permeable membrane and a micro-porous membrane placed one upon another. However, the permeability of O.sub.2 gas can not be expected in these membranes.
Disclosure of the Invention
An object of this invention is to provide a separator for alkali-zinc battery, which has both properties of a semi-permeable membrane and a micro-porous membrane so that a dendrite short-circuiting can be avoided sufficiently and a decease in battery capacity can be controlled by making O.sub.2 gas to be permeable well.
This invention provides a separator for alkali-zinc battery comprising a micro-porous membrane having alkali resistance, a part of the porous membrane having a high hydrophilic property and the remainder having a water repellent property.
According to this invention, the precipitation of ZnO is sufficiently controlled in the part having the hydrophilic property because this hydrophilic property is highly durable. Consequently, the dendrite short-circuiting in battery can be avoided sufficiently. In the part having the water repellent property, O.sub.2 gas is highly permeable. Consequently, the decrease in battery capacity can be controlled.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a vertical sectional partial view showing a separator of embodiment 1 of this invention. FIG. 2 is a diagram showing cycle life characteristics of batteries using separators of embodiments 1, 2 and 3 of this invention and a battery using a conventional separator. FIG. 3 is a diagram showing a change in charge/discharge cycle number in case a when a ratio of pores filled with ion permeable resin to the entire pores is changed. FIG. 4 is a vertical sectional partial view showing the separator of the embodiment 2 of this invention. FIG. 5 is a view viewed in a direction of arrow V of FIG. 4. FIG. 6 is a plan view showing another example of the embodiment 2. FIG. 7 is a plan view showing a further another example of the embodiment 2. FIG. 8 is a vertical sectional partial view showing the separator of the embodiment 3 of this invention. FIG. 9 is a vertical sectional partial view showing another example of the separator of the embodiment 3. FIG. 10 is a vertical sectional view showing a further another separator of the embodiment 3 of this invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1
FIG. 1 is the vertical sectional view showing the separator of the embodiment 1 of this invention. In FIG. 1, 1 denotes a micro-porous membrane, and a membrane having a trade name of "CELGARD #3401" (made by DAIC
REFERENCES:
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patent: 3377203 (1968-04-01), Mobius et al.
patent: 3427206 (1969-02-01), Scardaville et al.
patent: 4287272 (1981-09-01), Machi et al.
patent: 4359510 (1982-11-01), Taskier
patent: 4804598 (1989-02-01), Jakovitz et al.
patent: 4957673 (1990-09-01), Schroeder et al.
Patent Abstracts of Japan vol. 13, No. 334 (M-855) (3682) 27 Jul. 1989 and JP-A-01 110 904 (Isuzu Motors Ltd) 27 Apr. 1989.
Bogauchi Takehito
Eguchi Yoshihiro
Kishimoto Tomonori
Yamane Mitsuo
Kalafut Stephen
Yuasa Corporation
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